1. Field of the Invention
This invention relates to accelerator mass spectrometry (AMS), wherein negative ions are formed from a sample to be analyzed and are accelerated in a tandem accelerator to a high-voltage terminal maintained at a high positive potential. A stripper within the high-voltage terminal converts the negative ions to a positive charge state and induces dissociation of all background molecules. After further acceleration and mass analysis, the particles to be analyzed are detected and their properties meausured.
2. Description of the Prior Art
During the pass twelve years, detection efficiency for long-lived isotopes has been dramatically improved by applying the techniques of Accelerator Mass Spectrometry (AMS). Using AMS, the presence of a radioactive nucleus is detected, not by waiting for it to make a radioactive transformation, but rather by searching for the unstable atoms themselves. The basic principles of AMS instrumentation have been described by Kenneth H. Purser in U.S. Pat. No. 4,037,100; by Kenneth H. Purser, R. B. Liebert and C. J. Russo in Radiocarbon 22, (1980) 794; and by Kenneth H. Purser, A. E. Litherland and H. E. Gove in Nuclear Instruments and Methods 162, 637 (1979). A recent review of AMS measurements, as applied to long-lived isotopes, has been provided by D. Elmore and F. M. Phillips in Science 236, 543 (1987).